Distance image capturing device and distance image capturing method

Abstract

A distance image capturing device according to the present invention includes a light source unit that emits radiation light into a measurement space which is a space to be measured, a distance image sensor that receives light including reflected light reflected from an object in the measurement space as incident light, accumulates charges generated by the incident light for each pixel, and generates a distance image formed from a charge amount of the charges accumulated for each pixel, and a distance image processing unit that stores a signal value based on a non-controlled charge regardless of a control of accumulating charges in the distance image sensor, from the charge amount in the distance image, and corrects and acquires a distance to the object in the space by using the stored signal value.

What is claimed is: 
     
       1. A distance image capturing device comprising:
 a light source unit configured to emit radiation light into a measurement space which is a space to be measured; 
 a distance image sensor configured to receive light including reflected light from an object in the measurement space as incident light, accumulate charges generated by the incident light for each pixel, and generate a distance image formed from a charge amount of the charges accumulated for each pixel; and 
 a distance image processing unit configured to store a signal value based on a non-controlled charge included in the charge amount regardless of a control of accumulating the charges in the distance image sensor, from the charge amount in the distance image, and correct a distance to the object in the space by using the stored signal value. 
 
     
     
       2. The distance image capturing device according to  claim 1 , wherein
 the distance image sensor includes 
 a photoelectric conversion element that collects the charges generated in accordance with the incident light, a charge accumulation unit that accumulates the charges in a frame cycle, and a pixel circuit that performs a control of accumulating the charges in the charge accumulation unit, for each pixel, and 
 the distance image processing unit 
 subtracts an adjustment voltage corresponding to the charge amount of the non-controlled charge which is the charge flowing into the charge accumulation unit regardless of the control by the pixel circuit, from an input voltage corresponding to the charge amount accumulated in the charge accumulation unit, and measures a distance between the distance image sensor and the object. 
 
     
     
       3. The distance image capturing device according to  claim 2 , wherein
 the charge accumulation unit includes at least one first charge accumulation unit that accumulates a background light charge generated by receiving background light of the space and two or more second charge accumulation units that accumulate a reflected light charge generated by receiving the reflected light of the radiation light from the object. 
 
     
     
       4. The distance image capturing device according to  claim 3 , further comprising:
 a storage unit configured to store each of a reference background light voltage acquired from each of the first charge accumulation unit and the second charge accumulation unit by accumulating the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit, measured in advance in a state where the radiation light is not emitted under predetermined ambient light, and a reference standard voltage acquired from each of the first charge accumulation unit and the second charge accumulation unit without accumulating the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit. 
 
     
     
       5. The distance image capturing device according to  claim 4 , wherein
 the distance image sensor emits the radiation light into the measurement space, receives light including the reflected light from the object in the measurement space as incident light, and accumulates the charges generated by the incident light in each of the first charge accumulation unit and the second charge accumulation unit, and 
 the distance image processing unit divides a background light voltage generated by the charge accumulated in the first charge accumulation unit by the reference background light voltage measured in advance and stored in the storage unit to obtain an adjustment ratio, and calculates the adjustment voltage for each of the input voltages by multiplying each of the reference standard voltages by the adjustment ratio. 
 
     
     
       6. The distance image capturing device according to  claim 3 , wherein
 the frame cycle includes each of a first frame cycle and a second frame cycle, 
 in the first frame cycle, 
 the distance image sensor emits the radiation light into the measurement space, receives light including the reflected light from the object in the measurement space as incident light, and accumulates the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit, and 
 the distance image processing unit acquires the input voltage generated by the accumulated charges, and 
 in the second frame cycle, 
 the distance image sensor emits the radiation light into the measurement space, receives the light including reflected light from the object in the measurement space as the incident light, and does not accumulate the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit, and 
 the distance image processing unit acquires an adjustment voltage corresponding to the non-controlled charge in each of the first charge accumulation unit and the second charge accumulation unit. 
 
     
     
       7. The distance image capturing device according to  claim 3 , further comprising:
 a storage unit configured to store each of a reference reflected light voltage acquired from each of the first charge accumulation unit and the second charge accumulation unit by accumulating the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit, measured in advance in a state where the radiation light is emitted in a light-shielded environment, and a reference standard voltage acquired from each of the first charge accumulation unit and the second charge accumulation unit without accumulating the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit. 
 
     
     
       8. The distance image capturing device according to  claim 7 , wherein
 the distance image processing unit calculates each of the adjustment voltages for each of the input voltages by dividing a result obtained by adding each of the input voltages generated by the charges accumulated in each of the first charge accumulation unit and the second charge accumulation unit by a result obtained by adding each of the reference reflected light voltages to obtain an adjustment ratio, and multiplying the reference standard voltage by the adjustment ratio. 
 
     
     
       9. The distance image capturing device according to  claim 3 , wherein
 the frame cycle includes each of a first frame cycle and a second frame cycle, 
 in the first frame cycle, 
 the distance image sensor emits the radiation light into the measurement space in a light-shielded environment, receives light including the reflected light from the object in the measurement space as incident light, and accumulates the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit, and 
 the distance image processing unit acquires the input voltage generated by the charges accumulated in each of the first charge accumulation unit and the second charge accumulation unit, and 
 in the second frame cycle, 
 the distance image sensor emits the radiation light into the measurement space in the light-shielded environment, receives the light including the reflected light from the object in the measurement space as the incident light, and does not accumulate the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit, and 
 the distance image processing unit acquires an adjustment voltage corresponding to the non-controlled charge by the charges in each of the first charge accumulation unit and the second charge accumulation unit. 
 
     
     
       10. The distance image capturing device according to  claim 3 , further comprising:
 a storage unit configured to store each of 
 a reference background light voltage acquired from each of the first charge accumulation unit and the second charge accumulation unit by accumulating the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit, measured in advance in a state where the radiation light is not emitted under predetermined ambient light, 
 a first reference standard voltage acquired as a reference standard voltage from each of the first charge accumulation unit and the second charge accumulation unit without accumulating the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit, 
 a reference reflected light voltage acquired from each of the first charge accumulation unit and the second charge accumulation unit by accumulating the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit, measured in advance in a state where the radiation light is emitted in a light-shielded environment, and 
 a second reference standard voltage acquired as a reference standard voltage from each of the first charge accumulation unit and the second charge accumulation unit without accumulating the charges controlled by the pixel circuit in each of the first charge accumulation unit and the second charge accumulation unit. 
 
     
     
       11. The distance image capturing device according to  claim 10 , wherein
 the distance image sensor emits the radiation light into the measurement space, receives light including the reflected light from the object in the measurement space as incident light, and accumulates the charges generated by the incident light for each pixel, 
 the distance image processing unit divides the input voltage generated by the accumulated charges by the reference background light voltage that is measured in advance and stored in the storage unit to obtain a first adjustment ratio as an adjustment ratio, and calculates a first adjustment voltage for each of the input voltages by multiplying each of the first reference standard voltages by the first adjustment ratio, and 
 divides a result obtained by adding each of the input voltages by an addition result obtained by adding each of the reference reflected light voltages to obtain a second adjustment ratio as an adjustment ratio, calculates each of second adjustment voltages for each of the input voltages by multiplying the second reference standard voltage by the second adjustment ratio, and adds the first adjustment voltage and the second adjustment voltage to calculate the adjustment voltage. 
 
     
     
       12. The distance image capturing device according to  claim 3 , further comprising:
 a storage unit configured to acquire each of 
 a reference background light voltage acquired from each of the charge accumulation units by accumulating the charges controlled by the pixel circuit in each of N (N is an integer of 3 or more) charge accumulation units, measured in advance in a state where the radiation light is not emitted under predetermined ambient light, 
 a first reference standard voltage acquired as a reference standard voltage from each of the charge accumulation units without accumulating the charges controlled by the pixel circuit in each of the charge accumulation units, 
 a reference reflected light voltage acquired from each of the charge accumulation units by accumulating the charges controlled by the pixel circuit in each of the N charge accumulation units, measured in advance in a state where the radiation light is emitted in a light-shielded environment, and 
 a second reference standard voltage acquired as a reference standard voltage from each of the charge accumulation units without accumulating the charges controlled by the pixel circuit in each of the charge accumulation units, and configured to store each of 
 a reference background light control voltage corresponding to a charge amount of a controlled charge generated by the background light, collected in the photoelectric conversion element, distributed to and accumulated in each of the N charge accumulation units, obtained from each of the reference background light voltage and the first reference standard voltage, 
 a reference background light non-controlled voltage corresponding to a charge amount of a non-controlled charge generated by the background light and flowing into each of the N charge accumulation units without being distributed, 
 a reference reflected light control voltage corresponding to a charge amount of a controlled charge generated by the reflected light, collected in the photoelectric conversion element, distributed to and accumulated in each of the N charge accumulation units, and 
 a reference reflected light non-controlled voltage corresponding to a charge amount of a non-controlled charge generated by the reflected light and flowing into and accumulated in each of the N charge accumulation units without being distributed. 
 
     
     
       13. The distance image capturing device according to  claim 12 , further comprising:
 a distance calculation unit configured to 
 calculate and obtain a first ratio as a ratio of a light amount of background light in the environment in which the measurement is performed in advance obtained from a portion or all of the reference background light voltage, the first reference standard voltage, the reference background light control voltage, and the reference background light non-controlled voltage, stored in the storage unit, in a state of capturing the distance image, to a light amount of background light in the capturing state, calculate and obtain a second ratio as a ratio of a light amount of reflected light in the environment in which the measurement is performed in advance obtained from a portion or all of the reference reflected light voltage, the second reference standard voltage, the reference reflected light control voltage, and the reference reflected light non-controlled voltage, stored in the storage unit, to a light amount of reflected light in the capturing state, and 
 solve a simultaneous equation obtained by using each of the first ratio and the second ratio to calculate a reflected light control voltage corresponding to a charge amount of a controlled charge generated by the reflected light in the capturing state and accumulated in the charge accumulation unit thereby obtaining a distance to the object. 
 
     
     
       14. The distance image capturing device according to  claim 3 , further comprising:
 a storage unit configured to obtain each of 
 a reference reflected light voltage corresponding to a charge amount including a controlled charge accumulated by distribution, by performing a control of accumulating and distributing in each of the N charge accumulation units, and a non-controlled charge flowing into and accumulated regardless of the distribution, measured in advance in a state where the radiation light is emitted in a light-shielded environment, and 
 a second reference standard voltage acquired as a reference standard voltage corresponding to a charge amount of a non-controlled charge flowing into and accumulated without being controlled to be accumulated in each of the charge accumulation units, and 
 configured to store each of 
 a reference reflected light control voltage corresponding to a charge amount of a controlled charge generated by the reflected light, collected in the photoelectric conversion element, and distributed to and accumulated in each of the N charge accumulation units, obtained from each of the reference reflected light voltage and the second reference standard voltage, and 
 a reference reflected light non-controlled voltage corresponding to a charge amount of a non-controlled charge generated by the reflected light and flowing into and accumulated in each of the N charge accumulation units without being distributed. 
 
     
     
       15. The distance image capturing device according to  claim 14 ,
 wherein in an acquisition state for acquiring the distance, the frame cycle includes each of a first frame cycle and a second frame cycle, 
 in one of two frame cycles of the first frame cycle and the second frame cycle, the distance image sensor acquires a first reference standard voltage as a reference standard voltage corresponding to each of charge amounts of non-controlled charges accumulated in each of the N charge accumulation units without emitting the radiation light into the measurement space, 
 in the other of the two frame cycles, 
 the distance image sensor acquires a voltage for obtaining a distance, corresponding to a charge amount including each of a controlled charge accumulated by distribution from each of the charge accumulation units by emitting the radiation light into the measurement space and performing a control of distributing charges in each of the N charge accumulation units and a non-controlled charge flowing into regardless of distribution, and 
 the distance image capturing device further comprises a distance calculation unit configured to calculate and obtain a ratio of a light amount of reflected light in the environment in which the measurement is performed in advance obtained from a portion or all of the reference reflected light voltage, the second reference standard voltage, the first reference standard voltage, and the voltage for obtaining the distance, stored in the storage unit, to a light amount of reflected light in the acquisition state, and solve a simultaneous equation to calculate a reflected light control voltage corresponding to the charge amount of the controlled charge thereby obtaining a distance to the object. 
 
     
     
       16. The distance image capturing device according to  claim 3 , wherein
 when acquiring the distance in a light-shielded environment or a dark environment in which ambient light is negligible, the frame cycle includes each of a first frame cycle and a second frame cycle, 
 in one of two frame cycles of the first frame cycle and the second frame cycle, 
 the distance image sensor acquires a second reference standard voltage from each of the charge accumulation units by emitting the radiation light, receiving incident light from the measurement space, accumulating non-controlled charges that flow into each of the N charge accumulation units without accumulating the charges controlled by the pixel circuit, 
 in the other of the two frame cycles, 
 the distance image sensor acquires a reference reflected light voltage, which also serves as a voltage for acquiring a distance corresponding to the charge amount including each of the non-controlled charge and the controlled charge accumulated by being controlled by the pixel circuit, by emitting the radiation light, receiving the incident light from the measurement space, distributing and accumulating the charges from the photoelectric conversion element in each of the charge accumulation units by the control of the pixel circuit, and the distance image capturing device further comprises a distance calculation unit configured to solve a simultaneous equation using the second reference standard voltage and the reference reflected light voltage to calculate only a reflected light control voltage corresponding to the charge amount of the controlled charge thereby obtaining a distance to the object. 
 
     
     
       17. The distance image capturing device according to  claim 1 , further comprising:
 a lens configured to receive the incident light from the space, wherein 
 the distance image sensor receives the incident light via the lens. 
 
     
     
       18. The distance image capturing device according to  claim 5 , further comprising:
 a lens configured to receive the incident light from the space, wherein 
 the incident light is incident on each of the pixels via the lens, and the pixels for which the adjustment ratio is within a predetermined difference range are divided into groups in correspondence with a characteristic of the lens, and a median value of the reference standard voltages in the group is set as a reference standard voltage for all the pixels in the group. 
 
     
     
       19. The distance image capturing device according to  claim 5 , wherein
 the incident light is incident on each of the pixels via the lens, and a plurality of characteristics of the lens are stored in the storage unit in correspondence with the characteristic of the lens. 
 
     
     
       20. The distance image capturing device according to  claim 5 , wherein
 the incident light is incident on each of the pixels via the lens, and an adjustment function that outputs the adjustment ratio corresponding to each of positions of the pixels is stored in the storage unit in correspondence with characteristic of the lens. 
 
     
     
       21. A distance image capturing method comprising:
 a distance image generation process of, by a distance image sensor, emitting radiation light into a measurement space which is a space to be measured from a light source unit, receiving light including reflected light from an object in the measurement space as incident light, accumulating charges generated by the incident light for each pixel, and generating a distance image having a charge amount of the charges accumulated for each pixel; and 
 a distance image processing process of acquiring a distance to the object in the space from the charge amount in the distance image, by a corrected charge amount obtained by removing a non-controlled charge included in the charge amount regardless of a control of accumulating the charges in the distance image sensor.